For my embedded systems course we had to design an audio key and locking system, basically the system comprised of a device that would function as a key where the key would play a specific sound. The sound would be recognised by the audio lock and if the correct sound was played the lock would unlock. For the project we had approximately six weeks to design, test and deploy this system.
My team consisted of myself Jarred Martin, Lutando Ngakwakaza, Glenn Lauwo and Dirtiro Maubane. My role in the group was to do the interfacing between the various hardware components, test the suitability of the components and do the soldering.
The hardware we chose to do the project with was
- Cypress PSoC 3 kit microcontroller
- 4 x 3 Hexadecimal keypad
- 16 x 2 LCD screen
- Electret microphone
The PSoC 3 microcontroller was the only microcontroller we had used prior to starting this project so thats why decided to use it for the project.
The tools we used were
- Agilent oscilloscope
- Function generator
- Soldering iron
Initially we decided that the audio lock would record the sound that a user would want to use to open the door, but the PSoC 3 has only 256KB of flash memory. That is enough space to record only a few seconds of low quality audio. We ditched that in favour of on the fly processing signals processing so we wouldnt have to store any sounds on the PSoC 3, our code that would accomplish this performed a Fast Fourier Transforms on the incoming filtered audio signal. This worked well but was a bit slow since the PSoC is clocked at only 24 Mhz
Here is a slideshow of photos taken during development
This is what the final system looked like